CH/S4C CIT/Oct. 2005
MULTI-MEDIA PRODUCTION (CH. 1-2)

Basic Multimedia Elements
i.
Text
ii.
Graphics
iii.
Animations
iv.
Sound
v.
Video
Text (p. 2-5, 23-24)
Merits of Text:

Text is used in conveying messages in an accurate and unambiguous way.

Compared to other multimedia elements, text is much
smaller in size (1 byte for 1 English character, 2
bytes for 1 Chinese character) → takes up
smaller amount of store and is transmitted quickly.
Codes for Characters


ASCII (American Standard Codes for Information Interchange).
i.
Text in English are stored in ASCII codes.
ii.
ASCII codes can encode a total of 256 (28) characters, including English alphabets (both upper and lower
cases), Arabic digits and some common symbols.
Big-5, GB (GuoBiao), HZ (Hanzi).
i.
Text in Chinese are not stored in one single standard codes.
ii.
They can code at most 65536 (216) characters.
iii.
For a web page that consists of Chinese characters, the web page constructors must specify the character
set used in order to ensure that the users’ browsers can display the text properly.
Formatting Features

Character Formatting. It determines the appearance of characters, like colour, typeface, font size and font
style.

Paragraph Formatting. New paragraphs are created by pressing the
spacing, paragraph width and text alignment.

Page Formatting. It specifies the size of paper used, orientation (landscape/portrait), margins, header and
footer.
Enter
key.
It includes line
Text Document Formats

Text file (.txt). The files contain text codes only, without any formatting code. Thus it can be edited in all
kinds of editors.
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
Word Processing Document (.doc). The files can be edited easily. The formatting codes are softwarespecific.

Portable Document Format (.pdf). The files cannot be edited. The plug-in player to view the documents
can be downloaded freely. The original format of the source document is preserved.
Creating Text Methods

Typing through keyboard. For Chinese, special input methods like (Changjei, Quick, Phonetic, etc) are
used.

Scanning and then using OCR. Image of text is first captured by a
text by an OCR (Optical Character Recognition) software.

Handwriting (手寫板). A handwriting recognition device is used. It consists of a touch sensitive plate and
a handwriting recognition software.

Speech. Voice is captured by a microphone and a sound card. The text is then produced by a voice
recognition software.
scanner and then changed to
Note that the correctness of spelling can be checked by most word processors. They checks your document for
spelling errors by using their main dictionaries, i.e. a file containing most common words. (Refer to notes of
Microsoft word.
Graphics (p. 5-7, 25-30)

Computer graphic images are usually captured
i.
using digital devices, e.g. stills from
digital video recorder
.
ii.
using
iii.
from screen images by pressing the
various applications.
iv.
from clipart and stock photographs from CD-ROMs or web pages.
v.
from computer drawing using various graphics programs, e.g. Paintbrush (小畫家), Flash, etc.
scanners
digital camera
or individual frames of a video from
Print Screen
key and then pasted on documents of
.

Pixel. A pixel is the name given to a PICture Element, and refers to the smallest element used for building
up a picture in a particular graphics mode.

Bitmap graphics. Under this system, images are represented as an array of pixels of various colours, e.g.
images obtained from digital camera.

Vector graphics. Under this system, images are geometric objects such as straight lines, ovals and arcs, e.g.
graphs drawn with drawing tools of Word.
**Note that each vector graph can be resized and rotated without distortion and stored in smaller file size,
while a bitmap graphs is more photo-realistic.
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
Resolution. The quantities given to show how many pixels are found on an output or monitor. e.g. many
monitors now are of 1024 x 768 pixels. The higher the resolution, the higher the output quantity is.

Printing Resolution. It is measured in dpi (dot per inch), i.e. density of dots. It is usually smaller than that
appears on the screen. (Minimum printing resolution may be 150 dpi while that of screen may be around 72
dpi.)

The colours on the screen are based on the fact that all colours can be made up by a mixture of just three
primary colours namely
Red
, Green
and Blue
(RGB), i.e. mixing with lights
instead of paints.

For bitmap graphics,
i.
Image size. The number of pixels a bitmap graph has.
ii.
Colour depth. The number of different colours can be assigned to each pixel.
Figure 1: Open a jpeg file using Microsoft Image Editor, then choose properties (屬性) under the file (檔
案) menu, the following dialog box will be displayed,
Image size:
1024 x 768 pixels
Colour depth:
224 = 16777216
Different file format for bitmap graphics,

Bitmap( BMP

Joint Photographic Experts Group ( JPG
). Lossy compressed format, i.e. not capable to get back
the original uncompressed format. Suitable for compressing photos.

Graphics Interchange Format (
animation.

Portable Network Graphics (
). Uncompressed format.
GIF ). Lossless compressed format. Suitable for drawings. Supporting
PNG
). Similar to GIF. Smaller file size but do not support animation.
Figure: If you save a bitmap graphic file as a different file format using Photoshop Elements, one of the
following dialog boxes with different options would be displayed as follows,
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For .gif files
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**Note that text on some web pages were saved in graphic format. Why?
The text format can be shown exactly even the file is opened by different browsers. Moreover, more special
effects can be added to the text to make it more attractive.
Sound (p. 8-9, 31-35)
Nature of sound

When we make a sound, vibrations, called
sound waves
, are created as follows,
wavelength
amplitude
time

A sound is characterized by

The Loudness, or volume, is related to the height of the wave, i.e.
peaks, the louder the sound is.

The pitch is related to the
frequency . The higher the frequency, the higher the pitch is. It is measured
in hertz (Hz), i.e. number of vibrations in 1 second.
loudness and
pitch
.
amplitude
. The higher the wave
Sampling


Digitisation
of sound.
The height of the curve, the amplitude, is measured many times per second.
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
Sampling rate: the number of times a sample is taken for each time interval.

Sample size: the amount of information stored for each sample of a time interval.

The higher

The rule of sampling: Sample Rate > 2 x Maximum Sound Frequency.

E.g.
the sampling rate and the larger
Audio CD
FM broadcast
AM broadcast
sampling size, the higher the sampling quality will be.
Sampling rate (bit)
16
8
8
Sample size (K
44
22.05
11.025
MIDI (Musical Instrument Digital Interface)

It stores the musical notes of a music played by an instrument, such as a piano or a violin.

A computer connected to a MIDI keyboard can record the keystrokes and translate what are played into a written
score.

By using MIDI software, the musical notes from the score can be edited.

MIDI stores codes of musical notes only.  Small file size.
Preparing Sound Methods

Read-made

Recording using a
microphone

Recording
files using MIDI keyboard and other digital musical instruments.

Digitising analogue sound from various sources using a
sound clips
MIDI
from CD-ROM or the web.
and an audio recording program.
sound card
.
Animation (p. 12-14, 35-36)

An animation is made by showing discrete pictures one by one to give an illusion of continuous motion.
2-D and 3-D

Two-dimensional. It has two types:
i.
Cell
animation. Changing from one frame to another to give illusion of movement.
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Path
ii.

animation. Moving an object along a predetermined path on the screen.
Three-dimensional. It involves three steps:
i.
Modeling
. Creating 3-D objects.
ii.
Animation
. Defining motions.
iii.
Rendering
. Giving objects attributes like colors and textures..
Properties of an animation:

Frame Rate
i.
A
frame
is still picture displayed on the screen.
ii.
Frame rate determines the number of
iii.
The higher the frame rate, the smoother the animation is.

Type of Images. Vector graphic or bitmap graphic

Image Properties.

frames per second
i.
Bitmap graphic: image size, colour depth, transparency.
ii.
Vector-based animations are scalable.
(
fps).
Keyframes and Tweening
i.
A keyframe contains the object to be animated.
ii.
Tweening is filling up the frames between two keyframes.

Sound Effects

Looping. An animation starts over again
Preparing Animation Methods

Recording screen movement using a screen camcorder program.

Using a program specially designed to produce animation.
Two output format on the web:


Animated GIF.
i.
Independent bitmap images are stitched together by a software. No tweening.
ii.
Used for only small images.
iii.
Shown in any browser without any plug-ins
Animations of special format like Flash.
i.
The animated objects are vector-based.
ii.
Keyframes with objects are created and tweening between them is defined.
iii.
Plug-in must be installed in the user’s computer to play the animation.
Video (p. 12-14, 35-36)

A video is a full motion recording of an event.
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
Like animation, still pictures are shown successively to give an illusion of continuous motion.

Unlike animation, video begins with
continuous motion
and breaks it up into
still pictures .
Properties of a video

Frame rate. Frame rate determines the number of images displayed per second. (typical frame rate: 30 fps /
frames per second)

Image size. Usual image size for a video is 320 x 240 pixels.

Colour depth.

Sound sampling size and rate.
Video capture card


Analogue and digital.
i.
Digital video source: Digital video camera and video clips from CD-ROM or the web.
ii.
Analogue video source: Television broadcasting and video cassette recorder.
Analogue video signals are sent to the computer through a video capture card, which converts the analogue
signals into digital signals, and thus can be processed by the computer.
Compression of video

Compression of video is necessary for reducing
the Internet.

The standardized compression technique is Moving Picture Expert Groups (MPEG).

Other video format: AVI, MOV.

It may still take too long time to download a entire compressed video file on the Internet.
Video
streaming
allow the client browser start displaying the video before entire file has been transmitted.
(Sample file type: ASF, WMV, RM)
file size and enabling
live broadcast
on
Sources of Video

Digital

Recording video using digital devices like digital video recorder or digital camera..

Capturing video from various analogue video source (e.g. TV signals) using video capture cards.
video clips
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from CD-ROM or the web.
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